1. Field of the Invention
The present invention relates to a bonding apparatus and more particularly to a bonding apparatus which is suitable for use in bonding of a workpiece that has a large bonding area.
2. Prior Art
Bonding apparatuses that perform bump formation, wire connections, etc. are generally divided into two types: a vertically driven type and a supporting-point swinging type.
In the vertically driven type, a slider is installed on a linear guide that has vertical guide parts so that this slider can move upward and downward, an ultrasonic horn which holds a capillary is attached to a horn holder, and the horn holder is fastened to the slider. This type of vertically driven type apparatus is described in, for instance, Japanese Patent No. 3220483 (corresponding to Japanese Patent Application Laid-Open No. 05-74838).
In the second type, which is the supporting-point swinging type, an ultrasonic horn holding a capillary is attached to a horn holder. The horn holder is caused to swing about the supporting point of a cruciform plate spring that supports the horn holder, or the horn holder is fastened to a supporting shaft which is rotatably supported; and the horn holder is caused to swing about this supporting shaft. This type of supporting-point swinging type apparatus is disclosed in, for instance, Japanese Patent Nos. 2814154 (corresponding to Japanese Patent Application Laid-Open No. 04-317343) and 2860650 (corresponding to Japanese Patent Application Laid-Open No. 10-74785).
In the vertically driven type, the length of the linear guide must be long enough so that the capillary contacts the workpiece, and the linear guide extends below the horizontal plane of the bonding surface of the workpiece. Accordingly, the workpiece is limited to a size that does not contact the linear guide. Furthermore, since the driven part is heavy since it includes the ultrasonic horn, horn holder, slider, etc., the inertia is large when the apparatus is driven upward and downward at a high speed. As a result, bonding of small balls is especially difficult.
In the second supporting-point swinging type, the capillary must be perpendicular to the workpiece in the state in which the capillary contacts the workpiece. Accordingly, the supporting point or supporting shaft that constitutes the center of rotation of the horn holder must be at the same height as the tip end of the capillary. Consequently, the horn holder and the supporting point or supporting shaft are positioned on the horizontal plane of the bonding surface of the workpiece, so that the size of the workpiece is limited as in the case of the above-described first vertically driven type. Furthermore, since the capillary swings about the supporting point or supporting shaft, correction in the forward-rearward direction (axial direction of the ultrasonic horn) is necessary in order to move the capillary upward and downward substantially perpendicularly.